1. Field of the Invention
The present invention relates to a method for producing a multi-colored shaped body for further processing to form a dental restoration, and to an article produced thereby.
2. Description of the Related Art
The background to the invention is the sector of dental engineering, where the dental restoration, for example a dental crown, an inlay, an onlay or a veneer, is produced from a ceramic shaped body or a plastic shaped body. This production is increasingly carried out using machines, suitable processes being the CAD/CAM process or the copy-milling process.
In order to satisfy aesthetic requirements and to achieve dental restorations whose coloring does not differ, or scarcely differs, from the color, or even discolorations, of natural teeth, multicolored shaped bodies are produced.
EP 0 455 854 A1 discloses, for example, a ceramic shaped article made from customary ceramic or porcelain material having a plurality of differently colored layers ranging from vitreously translucent in the occlusal region to yellowish opaque in the cervical region. However, this document does not reveal any details as to how the multilayered, multicolored shaped article is produced.
Furthermore, U.S. Pat. No. 4,970,032 discloses a multicolored plastic shaped article having predetermined, varying colored layers, which are arranged above one another around a core. An injection-molding process is used to produce the core and the layers. The result is a block whose colored layers are clearly demarcated from one another, a fact which is incompatible with any approximation of the natural color of a tooth.
Based on this prior art, the object of the invention is to provide a method for producing a multicolored shaped body for further processing to form a dental restoration, which method can be used both for ceramic shaped bodies and for plastic shaped bodies, is cost-effective and allows a continuous color transition.
With regard to the method, the abovementioned object is achieved by means of the features of the present invention, in accordance with which at least two starting materials of different colors are introduced into a compacting die, which essentially predetermines the shape of the shaped body, and are pressed to form the shaped body.
According to the invention, it is recognized that the color transition can be set in an optimum manner, in accordance with the high demands placed on the aesthetics of the color of the tooth, irrespective of the starting material if the starting materials are pressed together. The contact surfaces are subjected to pressure, and the differently colored starting materials are brought into intimate contact in the interface region, so that minglingxe2x80x94even if only slightxe2x80x94takes place in that area. This mingling, which can be affected by the shape and size of the particles of the starting materials and/or by the pressure applied, enables a flowing color transition to be achieved and means that the actual interface between the starting materials is not visible. On the other hand, the pressing process may optionally also be used to produce color regions which are clearly delimited from one another. The use of the pressing process allows both plastic and ceramic to be used as starting materials at low costs, owing to reduced preparation expenditure.